Granular cork-polyurethane composition and products thereof

ABSTRACT

Cork Particles and a polyurethane resin are combined in a new composition. The mixture of cork particles with a liquid resin initially provides a free-flowing material which is easily handled without agglomeration. The mixture, when molded by the application of heat and pressure, produces a light weight, resilient, porous substance having a wide variety of uses such as innersoles for shoes and the like.

United States Patent [191 King a 1 GRANULAR CORK-POLYURETHANE COMPOSITION AND PRODUCTS THEREOF [75] Inventor: Robert E. King, Georgetown, Mass.

[73] Assignee: Cushioned Products Corporation,

Boston, Mass.

[22] Filed: Apr. 6, 1972 [21] Appl. N0.: 241,808

Related US. Application Data [63] Continuation of Ser. No. 491,402, Sept. 29, 1965, abandoned, and a continuation of Ser. No. 605,992, Dec. 30, 1966, abandoned, and a continuation of Ser.

No. 17,300, March 6, 1970, abandoned.

[52] US. Cl 260/9, 36/30 A, 36/37, 117/100 A, 161/211, 264/45, 264/54 [51] Int. Cl.....- C08g 51/20 [58] Field of Search 260/9; 264/45, 46, 54; 161/211; 117/161 KP, 148, 100 A; 36/30 A,

[56] References'Cited a UNlTED STATES PATENTS 2,365,508 12/1944 Austin 260/9 .[111 3,821,135 [451 June 28, 1974 Davis 117/100 x Primary Examiner-William H. Short Assistant ExaminerEdward Woodberry Attorney, Agent, or- Firm'-Morse, Altman, Oates & Bello [57] ABSTRACT (fork particles and a polyure th ane resin are combined in a new composition. The mixture of cork particles with a'liquid resin initially provides a free-flowing material which is easily handled without agglomeration. The mixture, when molded by the application of heat and pressure, produces a light weight, resilient, porous substance having a wide variety of uses such as innersoles for shoes and the like.

3 Claims, No Drawings CROSS-REFERENCE TO RELATED APPLICATIONS This is a continuation application of US. application Ser. No. 491,402, filed Sept. 29, 1965 and now abandoned, and of US. application Ser. No. 605,992 filed Dec. 30, 1966, and now abandoned, and of US. application Ser. No. 17,300 filed Mar. 6, 1970 and now abandoned.

This invention relates to a novel composition of matter comprising cork particles and a polyurethane resin, to processes for making such composition, articles comprising such compositions, and to processes for making said articles.

Heretofore, cork has been employed with viscous binders to produce two different types of products; one where the cork content is no greater than the weight of the binder and, the second type, where the cork content exceeds the weight of the resinous binder. In the first type, the resulting product exhibits the properties of the resin, particularly with respect to resiliency and the cork primarily functions to lower the density of the resulting product, except, however, when used with poly (vinyl chloride) resin, the art teaches that it improves the resins shrinkage or expansion characteristics. In the second case, the properties of cork predominate over the resin, particularly when the resin weight is less than one-half the weight of cork. These products are generally highly agglomerated and very tacky, therefore difficult to handle. The above products can be molded in various shapes to produce articles of interest.

This invention is concerned with the manufacture of free-flowing particles of cork which are impregnated with polyurethane resin. These impregnated particles are substantially tack-free, i.e., they can be swirled about in a glass container for at least 2 minutes at room temperature (i.e., to C.) and poured out of the container with less than 2 weight per cent of the particles sticking to the container walls. In addition, the impregnated cork particles of this invention are essentially free of agglomerates, i.e., less than 2 weight per cent of the particles contain more than 2 agglomerated particles and less than 25 weight per cent of the particles contain agglomeration of any type. In the most desirable embodiment of this invention, the particles are free of agglomerates.

Agglomeration or agglomerates," as employed herein and in the claims, means the adhesion of at least two impregnated cork particles which cannot be separated to the individual particles by grinding between ones fingers. If more strenuous means than simple rubbing of the joined particles between one fingers is required to separate them, then the joined particlesare considered in accordance with this invention to be agglomerates or agglomerated, and, hence, in a state of agglomeration.

Another feature of the polyurethane impregnated cork particles of this invention is that they possess essentially the same bulking characteristics as the cork particles prior to polyurethane resin impregnation. Thus, the impregnated cork particles possess a bulking characteristic not more than 10 percent greater than the bulk characteristics of the cork-particles prior to impregnation. i

A further feature of the impregnated cork particles of this invention is that their weight typically does not exceed two times the weight of the cork particles prior to the impregnation, generally not greater than three- ,,quarters more than the weight of the non-impregnated cork particles.

The impregnated cork particles of this invention are essentially free on visual inspection of resin on its surface, clearly indicating that the resin content is adsorbed on the particle surface and absorbed internally in the particles within their many interstices and hollows.

Because of the above features, the polyurethane resin impregnated cork particles are easily handled. They can be poured like finely ground sand into molds and compressed with heat into many useful articles. Because the particles are essentially tack-free of agglomerates, molded articles can be produced which are extremely uniform and essentially, and preferably, free of large voids. Moreover, because the polyurethane resin is provided within the cork particles, the resulting molded article possesses essentially the resiliency and buoyancy of cork, even though the molded and compressed particles are tightly bonded together by the resin.

The cork useful in the practice of this invention may be of any of the conventionally used varieties. However, it is preferable that the cork particles possess a particle size capable of passing through a 2.5 mesh screen, U.S. Sieve Series standard, and be retained by a 325 mesh screen, U.S. Sieve Series standard. Most desirably, the particle size whould be between 5 mesh to mesh. As can be noted from the above, the cork particle size is not narrowly critical though best results are obtained when the average particle size is fairly uniform, e.g., falling within a micron spread.

Polyurethaneresin (s), as defined herein and in the claims, includes resinous and elastomeric polyurethanes, as well as prepolymers which can be converted to the desired polyurethane. Such polyurethanes are formed by the reaction of an organic polyisocyanate and active. hydrogen containing organic compounds as determined by the Zerewittinoff Method, Journal of the American Chemical Society, volume 49, page 3181 (1927).

Organic polyisocyanates useable in forming the polyurethane resin include, by way of example, the followmg: 2, 4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of the foregoing, m-phenylende diisocyanate, p-phenylene diisocyanate, bis (4-isocyanatophenyl) methane, 2,2-bis (4-isocyanatophenyl)-propane, l, 6- hexamethylenediisocyanate, l ,4-tetramethylenediisocyanate, 4,4-methylenedi-ortho-tolylisocyanate, 2,4,4'-triisocyanatodiphenylether, toluene-2,3 ,6- triisocyanate, l-methoxy-2,4,6-benzenetriisocyanate, 4-chloro-m-phenylene-diisocyanate biphenyldiisocyanate, l,S-napthalenediisocyanate 1,4- cyclohexexanediisocyanate, stilbene diisocyanates, dixylylmethane diisocyanates, and the like. A significant list of suitable polyisocyanates useable herein is described by Siefl en, Annalen, 562 pages 122 to 135 (1949).

Active hydrogen containing organic compounds which may be reacted withthe organic polyisocyanates Thus an organic polyisocyanate can be reacted with alcoholic or phenolic hydroxyl groups which, in turn, are derived from or part of organic compounds, such as 1,4-dihydroxybenzene, catechol, pyrogallol, ethylene glycol, trimethylene glycol, 1,4-tetramethylene glycol, l,2-propylene glycol, 1,5-pentamethylene glycol, 1,6-hexamethylene glycol, l,2-butylene glycol, l,2- pentamethylene glycol, l,2-hexamethylene glycol, l,2- octamethylene glycol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, l,2,6'hexane triol, diethylene glycol, l,2-dipropylene glycol, di( 1,4- butylene) glycol, di(1,2-butylene) glycol, tri-and tetraethylene glycol, tri-and tetra-l,2-propylene glycol, triand tetra-1,4-butylene glycol, sucrose, cellulose, glucose, glycerol, pentaerythritol, and the like.

In addition, other most suitable hydroxy organic compounds include polyalkylene oxide diols such as poly (ethylene oxide) diol, and the like, having molecular weights in the range of from about 400 to 10,000 preferably from about 700 to 5,000. I

Other useable hydroxy organic compounds include the alkylene oxide adduct of active hydrogen containing compounds such as organic polyols and amines. These adducts are formed by the reaction of monomeric oxirane alkylene oxides with the polyols and/or amines in the presence of an alkaline catalyst suchas sodium and potassium hydroxides, N,N,N',N -tetramethylethylenediamine, ammonium hydroxide, tetramethylquaternary ammonium hydroxide, and the like. 11- lustrative alkylene oxides useable for adduct formation include ethylene oxide, l,2-propylene oxide, l,2- butylene oxide, 1,2-pentylene oxide, l,2-hexylene oxide, styrene oxide, and the like. Each adduct may contain from I to 100 or more of alkylene oxide units. Suitable organic polyols are encompassed by the hydroxy organic compounds described above. Useable amines for adduct formation include monoamines and polyamines suchas ammonia, hydrazine, N,N'-dimethyl hyrazine, urea, melamine, ethylene diamine, aniline, diethylene triamine, piperazine, methylamine, and the like. The above adducts may have molecular weights ranging from about 100 to about 5,000, and greater.

Another class of active hydrogen containing compounds which may also be classed as hydroxy organic compounds are the hydroxyterminated organic polyesters. These polyesters may be formed from the interreaction of organic polyols, such as described above, and organic polycarboxylic acid, or their esters and acid halides. By employing a molar excess of polyol over carboxylic acid, there is obtained a hydroxyterminated polyester. The amount of molar excess. will determine the molecular weight of the polyester. Instead of reacting carboxylic acidswith the polyol, one may employ instead an organolactone, such as caprolactone. The hydroxy group of the lactone serves as the chain terminator and, therefore, a molar excess of lactone is employed.

Illustrative of the polycarboxylic acids employable include, by way of example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkylsuccinic acids, maleic acid, fumaric acid, itaconic acid, citraconic acid, muconic acid, 1,2 and 1,4- cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydroterephthalic acid, tetrachlorophthalic acid, 1,5-naphthalene dicarboxylic acid, 1,1,5-pentanetricarboxylic acid, 1,2,4-hexanetricarboxylic acid, 1 ,2,3- propanetricarboxylic acid, l,2,4-benzenetricarboxylic acid, and the like.

Such polyesters desirably possess a molecular weight of from about 500 to about 10,000, or more. Preferably, the polyester has a molecular weight between about 700 and about 5,000.

The polyurethanes may be prepared in many ways. For example, a hydroxy containing compound and a polyisocyanate can be reacted to form a prepolymer containing free isocyanate groups. This prepolymer can then be reacted with any active hydrogen containing compound, such as water, amines, alcohols, diols, triols, polyols, or phenols, mercaptans, and the like, to form the final polyurethane. The active hydrogen compounds which are reacted with the prepolymer are termed herein to be chain-extenders. They function to react with the free isocyanate and link prepolymer moleculestogether to form the ultimate polymer.

Another technique of preparing the polyurethane involves forming a mixture of the hydroxy containing compound and the polyisocyanate, with or without a chain-extender. The mixture is heated to reaction temperature in the presence of conventional catalysts, such as tertiary amines, stannous octoate, dibutyltin dilaurate, and the like.

The above reactions and conditions employable are well known in the art and form no part of this invention.

In the practice of this invention, the prepolymer technique is preferred. However, regardless of the technique employed, the polyurethane and polyurethane forming reactants should be-in liquid state when mixed with the cork particles. Thus the polyurethane resin or reactants employed in making the resin should either be liquid or dissolved in a solvent when mixed with the cork particles. If a solvent is employed to dissolve the reactants, then it is evaporated from the impregnated cork prior to use thereof. If a chain-extender, such as water, is employed which is insoluble in the solvent, then the chain-extender may be admixed and absorbed in the cork particles after the solvent is evaporated.

Since cork is cellulosic and possesses hydroxyl groups, it is capable of reaction with isocyanates or hydrogen bonding with polyurethane resins. Thus, it'is believed that the cork enters into reaction with the polyurethane resin by covalent bonding and/or hydrogen bonding. This is believed to be the reason why the heatcompressed impregnated cork particles admirably bond to each other to form unique molded articles.

The cork particles are impregnated with the liquid polyurethane resin with or without chain-extender by dispersing the liquid into the cork until essentially all of the liquid is absorbed by the particles. Almost any mixing procedure may be employed. The liquid may be poured into a container containing the particles and mixing with any type of mixing device is continued until the desired amount of liquid is absorbed by the particles. If the polyurethane contains solvent, then the solvent is evaporated at relatively low temperature to minimize undesirable reaction. Highly volatile solvents are desirable to preclude premature reaction. Illustrative solvents include, e.g., acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, ethyl acetate, methyl acetate, isopropyl acetate, N,N-dimethylformanide, N,N-dimethylacetamide, chloroform, methylchloroform, diethyl ether, and the like.

Preferably, evaporation is conducted at reduced pressures serving to lower the effective temperature of evaporation.

The amount of resin by weight admixed and impregnated within the cork particles is preferably not in excess of the weight of the particles, and most desirably, does not exceed three-quarters the weight of the particles. If a solvent is employed, any amount maybe employed without adversely affecting absorbtion of the resin. However, it is desirable to admix and impregnate the particles with at least 5 weight per cent of the resin, based on the weight of the particles, and most preferably, at least 15 weight per cent of the resin.

To make the bonded and compressed cork articles of this invention, the resin impregnated particles may be placed into a mold of the desired shape and with pressure and heat, typically applied through the mold, the particles are compressed and bonded to the molds configuration. The time and temperature of molding is dependent upon the polyurethane resin employed, the cork particle size, the degree of compression and the like factors.

ln the usual case, the temperature during molding is at least about 35 up to about 300 C., and preferably, at least about 50 up to about 200 C. The residence time during molding is generally greater than about seconds up to about 10 minutes preferably greater than about 30 seconds up to about minutes. In the typical case, the higher the temperature employed, the lower the residence time needed to make the desired product.

One preferred embodiment of this invention involves the use of a polyurethane prepolymer possessing free isocyanate groups and incorporating this prepolymer with water in amounts of from about 0.5 to about 200 weight per cent, based on the weight of the prepolymer in admixture with the cork particles. Both the prepolymer and water are absorbed by the particles to form the desirable free-flowing impregnated particles of this invention. The particles may then by placed in a mold and heat-compressed to form a highly resilient, flexible cork article. It has been determined by heating the prea product possesses the resiliency of the foam and cork, the flexibility of the foam and low cost typified by cork alone.

The impregnated cork particles of this invention can be molded into many useful articles employing simple molding techniques. Typical molded articles include shoe innersoles, shoe outsoles, brassiere cups, acoustical paneling, stair treads, automobile headliners, automobile dash and/or crash panels, gaskets and seals, wall paneling, carpet underlay, floor tile, seat cushions, cold and hot temperature insulation panels, filters, liquid flotation equipment (life jackets, fishing bobs, etc.) and the like. The manufacture of such products is relatively simple. The desired amount of polyurethane resinimpregnated cork particles are poured uniformly in a mold cavity of the desired shape. Preferably, the walls of the cavity extend higher than the mold volume in which shaping takes place because the amount of impregnated cork placed in the mold desirably is sufficient to more than fill up such volume. Then a ram (male member) is forced into the cavity with sufficient force to compress the particles into the shaping volume. Since both the mold cavity and the ram are preheated or heated during compression, bonding (by thermoplastic adhesion or chemical reaction) of the particles occurs and, on removal of the article from the mold, there is obtained a permanently compressed cork article.

The resiliency and flexibility of the resulting article is dependentupon such features as the polyurethane resin employed (whether flexible or rigid); the amount of resin to the amount of cork employed; whether the resin is blown to form a foam; the cork particle size; the shape of the article; the molding conditions; and the like factors.

The following examples are intended to merely illustrate this invention and it is not intended that this invention shall be limited to the scope of these examples.

EXAMPLE I A polyurethane resin is employed and produced by reacting at C., with constant stirring, three (3) moles of bis (4-isocyanatophenyl) methane with one (1) mole of poly (l,4-tetramethylene oxide) diol hav ing an average molecular weight of l,650. The resulting resin is a liquid isocyanate end-blocked (or terminated) polyurethane prepolymer.

Cork particles having a particle size of and between 10 to 20 mesh, the above polyurethane resin and water, in the weight ratios of 2 to l to 1, respectively, are blended in the following manner; first the particles are placed in a suitably sized container and the specified amount of water is added; after stirring until the water is fully absorbed into the particles, during which time the particles appear to swell, the polyurethane resin is added and stirring is continued until the resin is fully absorbed by the particles.

The impregnated cork particles are deposited by hand in a cast steel mold possessing a cavity having the shape of a shoe innersole. The bottom surface of the cavity is contoured to the shape of the bottom of a foot thereby provided with depressed areas representing an arch support and the heel portion, and a raised area representing the support for the ball of the foot. The cavity mold is internally provided with cartridge heaters. The walls of the mold extended above the terminus ticles placed in the mold completely fills the cavity and the total surface of the radiating surface so that some of the particles are in contact with the extending walls. Above the mold, in a position aligned with the cavity is a movable ram, the bottom of which has a peripheral shape of the cavitys terminus and the same surface area as that of the opening to the cavity. The ram is also provided with cartridge heaters. Both the ram and cavity mold are heated to 90 C. prior to the addition of the particles.

The ram is then lowered to make direct contact with the terminus edge of the cavity, thereby forcing impregnated particles into the cavity and compressing the particles within the cavity. The ram is kept in this position for four minutes and then raised. The compressed polyurethane-impregnated cork innersole will be extremely resilient and flexible, the cork particles will be tightly interbonded, and the innersole will have an extremely light weight.

The above procedure is repeated except that the ram and cavity mold are heated to 140 C. The resulting innersole will be resilient, flexible and light weight. However, this innersole will be less resilient and flexible than the one produced at 90 C.

EXAMPLE ll The procedure of Example I is repeated except that the liquid polyurethane resin is produced by reacting one mole of poly (ethyleneadipate) chain-terminated by hydroxyl groups (formed by reacting adipic acid with a molar excess of ethylene glycol) and having an average molecular weight of 2,056, with 3.5 (three and one-half) moles of toluene diisocyanate (an isomeric mixture of 1,4- and 2,6-toluene diisocyanate) at 90 C. The resulting shoe innersole will be flexible, resilient, tough, and light weight.

EXAMPLE Ill The polyurethane resin employed in this example is Estane 5702 (produced by B. F. Goodrich Chemical Company, Division of B. F. Goodrich Company, Cleveland, Ohio) formed by reacting poly( 1,4- tetramethyleneadipate) diol, 1,4-butane diol and bis (4-isocyanatophenyl) methane, each provided in stoichiometric proportions and having the following physical properties:

Brittle Temperature Continued Property ASTM Number by impact (F.) D-l790 No Failures at F. Moisture Vapor Transmission gms/lOO in. /24 hours 1586 38 Properties obtained using 75 mil sheet.

* Extend at 20 inches/minute to 300%, hold 10 minutes, relax l0 minutes. 2.5 to 3.0 mil cost films.

'slot which is one-half inch thick. Both walls of the slot are 6 feet by 6 feet, 6 inches thick steel plates, one of which is stationary and the other movable toward and away from the other plate. Flushly fitted about the sides may be four slidable one-half inch thick steel plates, each 6 feet long and 12 inches wide, secured in aligned slots at the corners of the wall plates so that each onehalf inch thick plate can be slid across the space between the walls and the ends of the one-half inch plates abut. The abutting ends are greased. Both wall plates may be internally fitted with electrical cartridge heaters.

One of the one-half inch slidable plates is removed when the impregnated particles are poured in the slot and the slot is filled to its top with the particles. The slot is vertically aligned on top of a vibrating table and after the first filling of the slot, the slot is vibrated to shake down the particles, after which more particles are added to completely fill the slot. Then the remaining slidable plate is slid over the opening of the slot and both wall plates are heated to C. and the movable wall plate is adjusted to one-quarter inch from the other wall to make a one-quarter inch thick slot. After 5 minutes, the movable walls are removed from the stationary wall by a distance of 8 inches. The compressed 6 X 6 X A inch cork sheet is removed from contact with the stationary wall and may be placed in a mold having the shape of an automotive headliner. The mold may comprise matching male-female surfaces and internally may be provided tov take steam. The compressed cork sheet is placed in the mold and the mold is closed to one-fourth inch spacing between the matching surfaces thereby shaping the sheet to the configuration of the mold. After heating the mold to 150 C. the sheet is so shaped for 4 minutes.

The resulting headliner will be tough, self-supporting, heat-resistant, light and absorb sound.

A portion of one surface of the above headliner may be coated with a polyvinylchloride plastisol and the plastisol firmly bonded to the surface without prior sizing of the surface.

In making the foam impregnated cork articles of this invention, it may be found desirable to incorporate different additives to the polyurethane resin to assist or modify the type of foam formation. For example, one may add a surfactant such as a block polymer of a po- .lyalkyleneoxide and an organopolysiloxane, e.g., a silicone surfactant serving as a dispersant to improve foaming properties. Moreover, there can be added one of a wide choice of polyurethane foam catalysts, such as the catalysts mentioned above, or heat and light stabilizers to preclude premature yellowing and/or depolymerization of the polyurethane. The latter should be added as a matter of course to all of the polyrethane resins if yellowing is considered objectionable.

The polyurethane resins may be pigmented or dyed with conventional pigments and dyes, or filled with the conventional fillers. However, it is desirable that the pigments and fillers possess an average particle size of less than about one micron.

If it is desired, the shaped articles of this invention may be adhesively bonded to another layer of material,

such as fabric (woven, knitted and non-woven), wood,

metal, plastic, and the like. This can be achieved by pressing the layer of material into the shaped article and employing sufficient heat to soften the polyurethane resin. In many cases, the layer will be securely bonded to the article with only heat and pressure. Another and preferred technique involves placing the layer of material in contact with the impregnated cork particles when the particles are deposited in the mold cavity and then pressing the layer into the particles during the molding (or shaping) operation. The polyurethane resin is an excellent adhesive when employed in this manner. However, if it is undesirable to employ these techniques, then one can coat an adhesive on one l 10 ride-vinyl acetate copolymers, synthetic and natural rubber latexes and solutions, and the like.

Though the above description of this invention relates to many specific details, it is not intended that such details should act to limit this invention except to the extent provided in the claims.

I claim:

1. A molding composition suitable for forming shaped articles such as shoe insoles and the like, comprising a free-flowing particulate granular mixture of cork into which is substantially fully absorbed by substantially all of said cork particles predetermined proportional amounts of liquids consisting essentially of water, and a member selected from a group consisting of,

a. a solution of a polyurethane elastomeric resin in acetone,

b. a liquid isocyanate end-blocked polyurethane prepolymer possessing free isocyanate groups,

c. a liquid mixture of an organic polyisocyanate and an active hydrogen containing organic compound, said liquid mixture being reactable to form a polyurethane elastomeric resin, and

d. mixtures thereof, said cork particles having an average particle size between 2.5 mesh and 325 mesh, the weight of the members comprising 10 to of the weight of the cork particles, the amount of water being substantially equal by weight to the amount of said member.

2. A shaped article comprising the permanently compressed molding composition of claim 1.

3. The shaped article of claim 2 in the form of a shoe innersole. 

2. A shaped article comprising the permanently compressed molding composition of claim
 1. 3. The shaped article of claim 2 in the form of a shoe innersole. 